Method for preparing reversible addition-fragmentation chain transfer emulsion polymerization

Abstract

The invention discloses a method for preparing reversible addition-fragmentation chain transfer emulsion polymerization. The method comprises the following steps: adding 0.1 to 2.5 portions of amphiphilic macromolecular reversible addition-fragmentation chain transfer reagent, 20 to 40 portions of water and 1 to 20 portions of monomer by weight into a reactor, and stirring and mixing the mixture; introducing nitrogen into the reactor; heating the reactor to a temperature of between 50 and 80 DEG C; and adding 0.005 to 0.05 portion of water-soluble initiator by weight into the reactor to initiate polymerization for 0.5 to 6 hours. The method has the advantages of simple flow equipment, low energy consumption, easy removal of water system reaction heat, short reaction inhibition period, high reaction speed, high final percent conversion and good emulsion stability, and the amphiphilic macromolecular reversible addition-fragmentation chain transfer reagent can be used as a chain transfer reagent and an emulsifier without adding conventional emulsifier in addition, has actual molecular weight in accordance with a molecular weight design value and distribution of the molecular weight less than 1.4, can be synthesized into a segmented copolymer through semicontinuously adding the monomer, and has good industrial prospect.

Description

technical field [0001] The invention relates to emulsion polymerization, in particular to a preparation method for reversible addition scission chain transfer emulsion polymerization. Background technique [0002] Compared with other traditional polymerization methods, emulsion polymerization has many advantages: the polymerization reaction occurs in the latex particles dispersed in the water phase. Although the viscosity inside the latex particles is high, since water is the continuous phase, the viscosity of the whole system is not high. The viscosity of the system does not change much during the entire reaction process, which makes the heat transfer of the entire system easy; due to the free radical isolation effect, high reaction rates and high molecular weight polymers can be achieved simultaneously in emulsion polymerization; most Emulsion polymerization uses water as the dispersion medium, which avoids the trouble of expensive solvents and recycling solvents, and also...

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Problems solved by technology

However, efficient reversible addition scission chain transfer emulsion polymerization of styrene has not been achieved in practice: Gilbert et al. 1，2 People use polymethacrylic acid-polybutylacrylate amphiphilic macromolecular reversible addition chain scission chain transfer reagent to feed emulsion polymerization with starvation method, the process is complicated and the obtained molecular weight deviates greatly from the molecular weight design value; Charleux et al. 3 In 2008, polyethylene oxide macromolecular reversible addition chain scission chain transfer reagent was used for batch emulsion polymerization of styrene, and the final conversion rate was only 66.7% at 22.7 hours; other amphiphilic macromolecular reversible addition chain scission chain transfer Reversible addition chain scission chain transfer reagent 4 , A single-block reversible addition chain scission chain transfer reagent of ethylamine polydiethylmethacrylate 5 , Two-block reversible addition of poly(ethylene oxide) poly(diethylmethacrylate) ethylamine to chain scission chain transfer reagent 6 Batch emulsion polymerization of styrene failed to show any control over molecular weight and molecular weight distribution

The main problem of the current failure is that other people's amphiphilic macromolecular reversible addition chain scission and chain transfer reagents must be dissolved in water by adding alkali due to the inappropriate length ratio of hydrophilic and lipophilic segments, forming an aqueous phase. The pH value of the solution is ≥ 5.5, the result of the polymerization reaction is that the molecular weight is out of control, the molecular weight distribution is wide, the reaction polymerization inhibition period is very long, the reaction speed is slow, the final conversion rate is low, the emulsion is unstable, or one or more raw materials need to be added Add slowly during the polymerization process by dropping instead of adding directly before the reaction, etc.

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